The present invention relates to a seat for a vehicle that is equipped with an airbag unit at a side portion of a seat back.
Conventionally, a seat for a vehicle, for example, disclosed in U.S. Patent Application Publication Nos. 2004/0021304 A1, 2004/0124615 A1, and 2004/0130127 A1, in which an airbag unit is provided at a side portion of a seat back, and a bag member (airbag) is configured to inflate at a vehicle side crash to absorb a crash impact and thereby protect a passenger, is well known.
When the airbag unit is disposed at the side portion of the seat back, since the seat comprises a pad member and a seat skin covering the pad member, part of these pat member and seat skin that correspond to the airbag unit need to be torn or opened by an inflation pressure of the bag member so as to allow the bag member to inflate outside the seat.
Herein, in a case where the bag member is a small one having just a chest protection portion, part of the pad member and seat skin corresponding to the airbag unit may be opened promptly because the inflation pressure of the bag member is focused on this part properly, so that the bag member can inflate outside the seat properly.
Meanwhile, in a case where the bag member is configured to have a greater vertical length thereof so as to protect an entire upper body of the passenger, including the waist portion, like the bag member disclosed in the above-described patent publication, it may be rather difficult to make the bag member inflate properly at the same time over its entirely vertical length. Hereinafter, this situation will be described referring to an example. According to a certain seat, the thickness of a portion of the pad member that corresponds to a lower portion of the bag member (normally, a forward-projecting portion of the side support portion) is generally configured to be great (thick). Therefore, an inflation of the lower portion of the bag member tends to be delayed. This delay may happen to the airbag unit in which the bag member is covered by a flexible and easy-broken sheet member, such as a paper, not by a case. And, even though a port of inflatable gas from an inflator is provided at the lower portion of the bag member, the inflation of the lower portion tends to be delayed. Namely, in the case of the airbag unit in which the bag member is covered by the case, after the bag member has inflated to a certain degree in the case, the bag member goes out of the case and the increased inflation pressure of the bag member acts on the pad member and the seat skin over their entirely vertical length so as open them at the same time. In the case of the airbag unit in which the bag member is covered by the paper or the like, however, a specified portion of the bag member, which can easily inflate, for example, a relatively thin portion (a central portion or an upper portion of the bag member) tends to inflate earlier than any other portion of the bag member does. As a result, the inflation of the lower portion of the bag member is delayed.